Man Prime Offender Among Invasive Species

COLUMN

June 28, 2012|Robert M. Thorson

June seems to be the month for biological invasions. Last year it was the roadkill cougar in Milford. This year a black bear fell out of a tree in New Britain, and a moose was tranquilized in Plainville. These bits of newsworthy fun are ecologically trivial compared what happened on the Oregon coast earlier this month.

An "alien mother ship" arrived from Japan bearing more than100 tons of biological cargo exotic to our continent. More accurately, a 66-foot-long section of a floating dock torn loose by last year's Japanese tsunami docked near Neskowin, Ore., after a voyage of 15 months across the Pacific Ocean. Scraped from its concrete and steel hull during its stealth landing were many species of algae, crabs, starfish, microbes, snails, barnacles, worms, mussels, limpets and what not, which threaten the local coastal ecosystem. As I write, invaders are scampering and spreading in a country where the costs of invasive species exceed $100 billion per year.

These invasions — trivial and serious — got me to thinking about an earlier biological event that took place about 40,000 years ago in Australia. It was then that humans, an invasive species, first found their way to the island continent on a different kind of an alien ship. Within a few thousand years of human occupation, and completely independent of climate or other environmental changes, most species of large animals in Australia either went extinct or were decimated. Giant kangaroos, flightless birds and what looked like oversized wombats disappeared in a geological flash.

These events sent me scrambling to define an invasive species. Luckily, there's U.S. Executive Order 13112, which I quote in full: "An 'invasive species' is defined as a species that is: (1) non-native (or alien) to the ecosystem under consideration and (2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health. Invasive species can be plants, animals, and any organisms (e.g. microbes). Human actions are the primary means of invasive species introductions."

By this definition, the bears and moose are suburban invaders, but not invasive species. That more serious charge applies to the Connecticut colonials and other settlers who evicted these large mammals from their original home ranges. This invasion, which began with (or possibly before) the arrival of Christopher Columbus in 1492, refers both to the humans sailing the alien ships and to their biological cargo, which ranged from smallpox to African slaves.

Extending history to archaeology, the indigenous human populations of North America sometime before about 15,000 years ago were also invasive species, arriving in several waves perhaps over the Bering land bridge. Extending archaeology to geology, the massive exchange of flora and fauna that took place between North America and South America — when the Isthmus of Panama rose volcanically from the sea about three million years ago — led to invasions in both directions, the main consequence of which was the decimation of the indigenous South American biota.

Such exchanges of species between previously stable places is as natural as the Earth itself. Everything the fossil record tells us — from the first known microbe about 3.5 billion years ago to the ongoing mass extinction taking place today — makes this clear.

Equally natural are attempts to stop invasive species from getting a foothold. No natural breeding population willingly concedes its ancestral home to an alien invader. When coordinated and sophisticated, such territorial defense can be considered a chronic war, whether Visigoths vs. Imperial Rome or lake associations vs. invasive aquatic weeds.

War is indeed the right word for what biologists and bureaucrats are doing to prevent certain natural species from displacing others. They are guardians of the status quo, whether funded for selfish interests (economics, safety or recreational) or for broader ethical considerations of stewardship. Collectively, they constitute a Department of Defense against those that Homo sapiens have defined as the enemy.

At heart, and by definition, conservationists are conservatives. They are patriots to the cause of protecting the homeland.

And speaking of homeland, where was the Department of Homeland Security when something big enough to carry a boatload of terrorists landed without notice?

Robert M. Thorson is a professor of geology at the University of Connecticut's College of Liberal Arts and Sciences. His column appears every other Thursday. He can be reached at profthorson@yahoo.com.